The IAG spectral atlas of the spatially resolved Sun: Centre-to-limb observations

Abstract

Solar surface magneto-convection appears as granulation pattern that impacts spectral lines in terms of both shape and wavelength. Such induced effects also tend to vary over the observed solar disc because of the changing observation angle and, thus, the changing observation height as well. Centre-to-limb observations of the resolved Sun offer an insight into the variable spectral behaviour across different heliocentric observing positions, providing crucial information about limb darkening, convective velocities, and line profile variability relevant to radial velocity (RV) calculations. Thus, RV measurements and exoplanet transit spectroscopy depend on precise reference templates. We want to provide a spectroscopic centre-to-limb solar atlas at high spectral resolution and high-frequency accuracy. The atlas shall help improve the understanding of the solar atmosphere and convection processes. We performed high-resolution observations of the resolved quiet Sun with a Fourier transform spectrograph at the Institut für Astrophysik und Geophysik in Göttingen. Our dataset contains a wavelength range from 4200Å to 8000Å. We obtained 165 spectra in total, with a spectral resolution of $\Delta \nu$ = 0.024cm${}^{-1}$, corresponding to a resolving power $R$ of 700,000 at $\sim$6000Å. We present a centre-to-limb solar atlas containing 14 heliocentric positions. To check for consistency, we investigated the FeI ~6175Å absorption line and compared our line profiles with previous centre-to-limb observations and also with simulations. The line profile and also the bisector profiles are generally consistent with previous observations, but we have identified differences to model line profiles, especially close to the solar limb.

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Cited by in corpus (16)

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• Convective characteristics of Fe I lines across the solar disc
• Solar center-to-limb variation in Rossiter-McLaughlin and exoplanet transmission spectroscopy
• GRASS II: Simulations of Potential Granulation Noise Mitigation Methods
• Probing Na in giant exoplanets with ESPRESSO and 3D NLTE stellar spectra
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• The CARMENES search for exoplanets around M dwarfs. The impact of rotation and magnetic fields on the radial velocity jitter in cool stars
• Towards 10 cm/s radial velocity accuracy on the Sun using a Fourier transform spectrometer
• Precise and efficient modeling of stellar-activity-affected solar spectra using SOAP-GPU
• High-spectral Resolution, Multi-wavelength Center-to-limb Observations of the Sun
• Solar Flux Atlases: The new HARPS-N Quiet Sun Benchmark and Ca II H & K Lines Continuum Normalisation
• Modeling HMI observables for the study of solar oscillations
• An Atlas of Spectroheliograms from 3641 to 6600 Å
• Towards understanding stellar variability at the sub m/s level: granulation-induced variability across the optical spectrum
• Exploring the surface of HD 189733 via Doppler shadow analysis of planetary transits